Information transmitting apparatus and method, information receiving apparatus and method, information transmitting and receiving system and method, recording medium and program

ABSTRACT

An original blanking period of a video signal is shortened to a set blanking period, and audio data is multiplexed into a resulting superimposing period. Table distinguishing data indicating the length of the superimposing period is inserted into the period as a blanking signal. With this configuration, it is possible to enable transmission and reception of an audio signal in a system capable of transmitting and receiving a video signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/724,770, filed Mar. 16, 2007, which is a continuation ofU.S. patent application Ser. No. 10/095,848, filed Mar. 12, 2002 andwhich claims priority from Japanese Application No. 2001-067969 filedMar. 12, 2001, the disclosures of which are hereby incorporated byreference herein.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus and a method fortransmitting information, an apparatus and a method for receivinginformation, a system and a method for transmitting and receivinginformation, a recording medium and a program, and particularly to anapparatus and a method for transmitting information, an apparatus and amethod for receiving information, a system and a method for transmittingand receiving information, a recording medium and a program that make itpossible to transmit audio data more efficiently by multiplexing theaudio data into video data.

A blanking period of video data is often used when the video data hasother data superimposed thereon for transmission. In teletextbroadcasting, text data is inserted into a vertical blanking period, forexample.

Since the blanking period is extremely short as compared with a periodfor transmitting original video data, however, types of data capable ofbeing multiplexed are limited to low-volume data such as text data.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and it isaccordingly an object of the present invention to enable efficienttransmission of data such as, for example, audio data which is low involume as compared with video data, but high in volume as compared withtext data or the like.

According to a first aspect of the present invention, there is providedan information transmitting apparatus including a first capturing unitoperable to capture a video signal; a second capturing unit operable tocapture a compressed audio signal; a setting unit operable to set ablanking period of the video signal to a predetermined period of alength different from an original period; a multiplexing unit operableto multiplex the compressed audio signal into a differential periodcorresponding to a difference between the blanking period of the videosignal and the predetermined period set by the setting unit; and a videosignal transmitter operable to transmit the video signal having thecompressed audio signal multiplexed therein.

The setting unit may set the blanking period to the predetermined periodby disposing a blanking signal representing the blanking period only inthe predetermined period other than the differential period of theblanking period of the video signal.

The blanking signal may form a control signal.

The information transmitting apparatus may further include a retainingunit operable to retain information on the differential period or thepredetermined period, and the multiplexing unit may multiplex thecompressed audio signal into the differential period on the basis of theinformation retained by the retaining unit.

The retaining unit may retain a correspondence between a type of thevideo signal and the differential period or the predetermined period asthe information on the differential period or the predetermined period.

The information transmitting apparatus may further include adistinguishing information transmitter operable to transmitdistinguishing information for distinguishing the differential period orthe predetermined period.

The distinguishing information transmitting unit may transmit thedistinguishing information in the predetermined period of the videosignal as a type of blanking signal representing a blanking period.

The distinguishing information transmitting unit may transmit thedistinguishing information in a vertical blanking period.

The distinguishing information transmitting unit may transmit thedistinguishing information via a transmission line different from atransmission line of the video signal.

The distinguishing information may be information allowing determinationof a period from a start point to an end point of the predeterminedperiod or a period from a start point to an end point of thedifferential period.

The information transmitting apparatus may further include a compressingunit operable to compress the audio signal.

The information transmitting apparatus may further include an encryptingunit operable to encrypt the audio signal by a method common with thevideo signal.

According to a second aspect of the present invention, there is providedan information transmitting method, including capturing a video signal;capturing a compressed audio signal; setting a blanking period of thevideo signal to a predetermined period of a length different from anoriginal period; multiplexing the compressed audio signal into adifferential period corresponding to a difference between the blankingperiod of the video signal and the predetermined period set by thesetting step; and transmitting the video signal having the compressedaudio signal multiplexed therein.

According to a third aspect of the present invention, there is provideda recording medium recorded with a computer readable program fortransmitting information, the program including capturing a videosignal; capturing a compressed audio signal; setting a blanking periodof the video signal to a predetermined period of a length different froman original period; multiplexing the compressed audio signal into adifferential period corresponding to a difference between the blankingperiod of the video signal and the predetermined period set by thesetting step; and transmitting the video signal having the compressedaudio signal multiplexed therein.

According to a fourth aspect of the present invention, there is provideda system for performing an information transmission process, including aprocessor for executing instructions; and instructions, the instructionsincluding capturing a video signal; capturing a compressed audio signal;setting a blanking period of the video signal to a predetermined periodof a length different from an original period; multiplexing thecompressed audio signal into a differential period corresponding to adifference between the blanking period of the video signal and thepredetermined period set by the setting step; and transmitting the videosignal having the compressed audio signal multiplexed therein.

According to a fifth aspect of the present invention, there is providedan information receiving apparatus including a receiver operable toreceive a transmitted signal; a first capturing unit operable to capturea video signal from the received signal; a detecting unit operable todetect a blanking period of the captured video signal, the blankingperiod being set to a length different from an original period; a secondcapturing unit operable to capture information on a multiplexing periodin which a compressed audio signal is multiplexed; a third capturingunit operable to capture the multiplexed compressed audio signal fromthe captured video signal on the basis of the captured information onthe multiplexing period; and a correcting unit operable to correct thedetected blanking period on the basis of the captured information on themultiplexing period.

The information receiving apparatus may further include a convertingunit operable to convert the compressed audio signal captured by thethird capturing unit into a continuous signal.

A blanking signal representing the blanking period may form a controlsignal.

The information receiving apparatus may further include a retaining unitoperable to retain the information on the multiplexing period, and thesecond capturing unit may capture the information on the multiplexingperiod from the information retained by the retaining unit.

The retaining unit may retain a correspondence between a type of thevideo signal and the multiplexing period as the information on themultiplexing period.

The information receiving apparatus may further include a distinguishinginformation extracting unit operable to extract distinguishinginformation for distinguishing the multiplexing period.

The distinguishing information extracting unit may extract thedistinguishing information from a blanking signal representing theblanking period, the blanking signal being inserted in the blankingperiod of the video signal.

The distinguishing information extracting unit may extract thedistinguishing information from the blanking signal in a verticalblanking period.

The distinguishing information extracting unit may extract thedistinguishing information from a signal received via a transmissionline different from a transmission line of the video signal.

The distinguishing information may be information allowing determinationof a period from a start point to an end point of the multiplexingperiod or a period from a start point to an end point of the blankingperiod being set to the length different from the original period.

The information receiving apparatus may further include an expandingunit operable to expand the compressed audio signal.

The information receiving apparatus may further include a decryptingunit operable to decrypt the audio signal by a method common with thevideo signal, the audio signal being encrypted by a method common withthe video signal.

According to a sixth aspect of the present invention, there is providedan information receiving method including receiving a transmittedsignal; capturing a video signal from the received signal; detecting ablanking period of the captured video signal, the blanking period beingset to a length different from an original period; capturing informationon a multiplexing period in which a compressed audio signal ismultiplexed; capturing the multiplexed compressed audio signal from thecaptured video signal on the basis of the captured information on themultiplexing period; and correcting the detected blanking period on thebasis of the captured information on the multiplexing period.

According to a seventh aspect of the present invention, there isprovided a recording medium recorded with a computer readable programfor receiving information, the program including receiving a transmittedsignal; capturing a video signal from the received signal; detecting ablanking period of the captured video signal, the blanking period beingset to a length different from an original period; capturing informationon a multiplexing period in which a compressed audio signal ismultiplexed; capturing the multiplexed compressed audio signal from thecaptured video signal on the basis of the captured information on themultiplexing period; and correcting the detected blanking period on thebasis of the captured information on the multiplexing period.

According to an eighth aspect of the present invention, there isprovided a system for performing information reception, including aprocessor for executing instructions; and instructions, the instructionsincluding receiving a transmitted signal; capturing a video signal fromthe received signal; detecting a blanking period of the captured videosignal, the blanking period being set to a length different from anoriginal period; capturing information on a multiplexing period in whicha compressed audio signal is multiplexed; capturing the multiplexedcompressed audio signal from the captured video signal on the basis ofthe captured information on the multiplexing period; and correcting thedetected blanking period on the basis of the captured information on themultiplexing period.

According to a ninth aspect of the present invention, there is providedan information transmitting and receiving system, including aninformation transmitting apparatus; and an information receivingapparatus; the information transmitting apparatus including a firstcapturing unit operable to capture a video signal; a second capturingunit operable to capture a compressed audio signal; a setting unitoperable to set a blanking period of the video signal to a predeterminedperiod of a length different from an original period; a multiplexingunit operable to multiplex the compressed audio signal into adifferential period corresponding to a difference between the blankingperiod of the video signal and the predetermined period set by thesetting unit; and a video signal transmitter operable to transmit thevideo signal having the compressed audio signal multiplexed therein; andthe information receiving apparatus including a receiver operable toreceive a signal transmitted from the information transmittingapparatus; a third capturing unit operable to capture the video signalfrom the received signal; a detecting unit operable to detect theblanking period of the captured video signal, the blanking period beingset to the predetermined period; a fourth capturing unit operable tocapture information on the differential period; a fifth capturing unitoperable to capture the multiplexed compressed audio signal from thecaptured video signal on the basis of the captured information on thedifferential period; and a correcting unit operable to correct thedetected blanking period on the basis of the captured information on thedifferential period.

According to a tenth aspect of the present invention, there is providedan information transmitting and receiving method, including capturing avideo signal; capturing a compressed audio signal; setting a blankingperiod of the video signal to a predetermined period of a lengthdifferent from an original period; multiplexing the compressed audiosignal into a differential period corresponding to a difference betweenthe blanking period of the video signal and the predetermined period setby the setting step; transmitting the video signal having the compressedaudio signal multiplexed therein; receiving the transmitted signal;capturing the video signal from the received signal; detecting theblanking period of the captured video signal, the blanking period beingset to the predetermined period; capturing information on thedifferential period; capturing the multiplexed compressed audio signalfrom the captured video signal on the basis of the captured informationon the differential period; and correcting the detected blanking periodon the basis of the captured information on the differential period.

According to an eleventh aspect of the present invention, there isprovided a recording medium recorded with a program for transmitting andreceiving information, the program including capturing a video signal;capturing a compressed audio signal; setting a blanking period of thevideo signal to a predetermined period of a length different from anoriginal period; multiplexing the compressed audio signal into adifferential period corresponding to a difference between the blankingperiod of the video signal and the predetermined period set by thesetting step; transmitting the video signal having the compressed audiosignal multiplexed therein; receiving the transmitted signal; capturingthe video signal from the received signal; detecting the blanking periodof the captured video signal, the blanking period being set to thepredetermined period; capturing information on the differential period;capturing the multiplexed compressed audio signal from the capturedvideo signal on the basis of the captured information on thedifferential period; and correcting the detected blanking period on thebasis of the captured information on the differential period.

According to a twelfth aspect of the present invention, there isprovided a system for performing information transmission and receptionprocesses, including a processor for executing instructions; andinstructions, the instructions including capturing a video signal;capturing a compressed audio signal; setting a blanking period of thevideo signal to a predetermined period of a length different from anoriginal period; multiplexing the compressed audio signal into adifferential period corresponding to a difference between the blankingperiod of the video signal and the predetermined period set by thesetting step; transmitting the video signal having the compressed audiosignal multiplexed therein; receiving the transmitted signal; capturingthe video signal from the received signal; detecting the blanking periodof the captured video signal, the blanking period being set to thepredetermined period; capturing information on the differential period;capturing the multiplexed compressed audio signal from the capturedvideo signal on the basis of the captured information on thedifferential period; and correcting the detected blanking period on thebasis of the captured information on the differential period.

The apparatus and method for information transmission, and the programaccording to the present invention, multiplex the compressed audiosignal into the differential period created by setting the blankingperiod of the video signal to the predetermined period.

The apparatus and method for information reception, and the programaccording to the present invention, capture the compressed audio signalsuperimposed in the multiplexing period of the received video signal,and correct the blanking period on the basis of the multiplexing period.

The system and method for information transmission and reception, andthe program according to the present invention, multiplex the compressedaudio signal into the differential period of the video signal, andthereby transmit the compressed audio signal from the informationtransmitting apparatus. The information receiving apparatus captures thecompressed audio signal multiplexed in the differential period, andcorrects the blanking period on the basis of the differential.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an informationtransmitting and receiving system to which the present invention isapplied;

FIG. 2 is a block diagram showing a configuration of a transmitter inFIG. 1;

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F are diagrams of assistance inexplaining signals input to the transmitter of FIG. 2;

FIG. 4 is a block diagram showing a configuration of a receiver in FIG.1;

FIG. 5 is a flowchart of assistance in explaining transmissionprocessing on a channel A of the transmitter of FIG. 2;

FIG. 6 is a diagram showing an example of blanking data;

FIG. 7 is a flowchart of assistance in explaining transmissionprocessing on a channel B of the transmitter of FIG. 2;

FIG. 8 is a flowchart of assistance in explaining transmissionprocessing on a channel C of the transmitter of FIG. 2;

FIGS. 9A, 9B, 9C, and 9D are timing charts of assistance in explainingthe transmission processing of the transmitter of FIG. 2;

FIGS. 10A, 10B, and 10C are timing charts of assistance in explainingthe operation on the channel A of the transmitter of FIG. 2 around ablanking period;

FIGS. 11A, 11B, and 11C are timing charts of assistance in explainingthe operation on the channel B of the transmitter of FIG. 2 around ablanking period;

FIGS. 12A, 12B, and 12C are timing charts of assistance in explainingthe operation on the channel C of the transmitter of FIG. 2 around ablanking period;

FIG. 13 is a flowchart of assistance in explaining reception processingon a channel A of the receiver of FIG. 4;

FIG. 14 is a flowchart of assistance in explaining reception processingon a channel B of the receiver of FIG. 4;

FIG. 15 is a flowchart of assistance in explaining reception processingon a channel C of the receiver of FIG. 4;

FIGS. 16A, 16B, 16C, and 16D are timing charts of assistance inexplaining operation of the receiver of FIG. 4; and

FIG. 17 is a block diagram showing another configuration of the digitaltuner of FIG. 2.

DETAILED DESCRIPTION

Preferred embodiments of the present invention will hereinafter bedescribed in detail with reference to the drawings.

FIG. 1 shows an example of a configuration of a transmitting andreceiving system to which the present invention is applied. A digitaltuner 31 receives a broadcast radio wave via an antenna 32, and suppliesa demodulated output to a monitor 33 through a TMDS (TransitionMinimized Differential Signaling) cord 34 (hereinafter described simplyas a TMDS 34) based on DVI (Digital Video Interface) standards. Thedigital tuner 31 is also connected to the monitor 33 by a DDC (DisplayData Channel) bus 35 (hereinafter described simply as a DDC 35) based onthe DVI standards.

The digital tuner 31 has a front end 41. The front end 41 demodulatesthe broadcast wave received via the antenna 32, and then outputs videodata and audio data (hereinafter also referred to as AV data) obtainedby demodulating the broadcast wave to an AV decoder 42. The AV decoder42 decodes the AV data supplied from the front end 41, and then outputsthe result to a transmitter 43. The transmitter 43 is controlled by acontrol unit 44, and outputs the AV signal supplied from the AV decoder42 to the monitor 33 via the TMDS 34.

The monitor 33 incorporates a receiver 51. The receiver 51 receives theAV data supplied from the transmitter 43 of the digital tuner 31 via theTMDS 34, and then separates audio data, video data, and synchronizingdata.

The audio data output from the receiver 51 is subjected to D/Aconversion by a D/A converter 52, and then output from left-channel andright-channel speakers 53 and 54.

The video data output from the receiver 51 is subjected to D/Aconversion by a D/A converter 55, amplified by an RGB amplifier 56, andoutput to a CRT 58.

An H/V sync generating unit 57 generates a horizontal synchronizingsignal and a vertical synchronizing signal on the basis of thesynchronizing data supplied from the receiver 51, and then supplies thehorizontal synchronizing signal and the vertical synchronizing signal toa driving circuit of the CRT 58.

FIG. 2 shows an example of a configuration of the transmitter 43. Pixeldata A, pixel data B, and pixel data C (for example blue (B), green (G),or red (R) pixel data as shown in FIG. 3A, 3B, or 3C, respectively) forthree channels A, B, and C, which data forms the video data output fromthe AV decoder 42, are supplied from terminals 80A, 80B, and 80C to theupper input terminals (as viewed in the figure) of switches 81A, 81B,and 81C, respectively. The pixel data of each of the colors (channels)for one pixel is expressed as data of 8 bits.

A terminal 91 is supplied with data of 2 bits forming horizontalsynchronizing data and vertical synchronizing data. The 2-bit data issupplied to an encoder 83A.

A terminal 92 is supplied with data of 2 bits forming a control signal(CTL0, CTL1) as shown in FIG. 3E, for example. The 2-bit data issupplied to an encoder 83B.

A terminal 93 is supplied with audio data, in this example, as data tobe superimposed (multiplexed). The audio data input from the terminal 93is stored temporarily by a buffer 84, and then supplied as data in unitsof 8 bits to the lower input terminal (as viewed in FIG. 2) of theswitch 81A, 81B, or 81C.

A terminal 94 is supplied with a blanking signal indicating a blankingperiod as shown in FIG. 3D. The blanking signal is supplied to a timinggeneration unit 85.

A terminal 95 is supplied with a pixel clock of 25 MHz to 165 MHz asshown in FIG. 3F. The pixel clock is supplied to a PLL circuit 87. Thepixel clock is in synchronization with each of the pixels of thechannels A, B, and C. The PLL circuit 87 generates a clock of afrequency ten times that of the input pixel clock in synchronizationwith the pixel clock, and then supplies the generated clock to thetiming generating unit 85. The PLL circuit 87 also outputs a stablepixel clock to the monitor 33.

The timing generating unit 85 generates a timing signal to control thebuffer 84, the switches 81A, 81B, and 81C, and encrypting units 82A,82B, and 82C in synchronization with the blanking signal and the pixelclock. The timing generating unit 85 also sets (shortens) the blankingsignal to a predetermined length, and supplies the set blanking signalto encoders 83A, 83B, and 83C.

The switches 81A, 81B, and 81C are each turned to the upper inputterminal or the lower input terminal in the figure on the basis of thetiming signal supplied from the timing generating unit 85 to select thepixel data A to C or the audio data. The switches 81A, 81B, and 81Coutput the selected pixel data or audio data to their correspondingencrypting units 82A, 82B, and 82C, respectively.

The encrypting units 82A, 82B, and 82C encrypt the video data (pixeldata) or the audio data input thereto by a common algorithm, and thenoutput the results to their corresponding encoders 83A, 83B, and 83C.

A superimposing period table 86 prestores data on length of a horizontalblanking period and length of a vertical blanking period correspondingto the pixel data to be output from the encoders 83A to 83C.

For example, when pixel data to be encoded and output is 480p (thenumber represents the number of scanning lines, and p denotes aprogressive system), the horizontal blanking period corresponds to alength of 138 pixels. When pixel data to be encoded and output is 720p,the length of the horizontal blanking period corresponds to 370 pixels.When pixel data to be encoded and output is 1080i (i denotes aninterlacing system), the length of the horizontal blanking periodcorresponds to 280 pixels.

That is to say, data for displaying position (length) of a horizontalblanking period and position (length) of a vertical blanking periodcorresponding to the displaying system are stored in the superimposingperiod table 86.

The timing generating unit 85 turns the switches 81A and 81C to thelower side thereof (as viewed in the figure) to select audio data for asuperimposing period (multiplexing period) stored in the superimposingperiod table 86.

During a period when the blanking signal set by the timing generatingunit 85 (hereinafter referred to as the set blanking signal) is notsupplied, the encoder 83A encodes the 8-bit pixel data A or audio datasupplied from the encrypting unit 82A on the basis of a predeterminedalgorithm, and then outputs the result as 10-bit data of the datachannel A.

During a period when the set blanking signal is input (hereinafterreferred to as a set blanking period), the encoder 83A encodes(generates) 10-bit blanking data on the basis of the 2-bit horizontalsynchronizing signal or vertical synchronizing signal input from theterminal 91, and then outputs the blanking data as data of the datachannel A.

As with the encoder 83A, during the period other than the set blankingperiod, the encoder 83B or 83C encodes the pixel data or audio datainput from the encrypting unit 82B or 82C, respectively, and thenoutputs the result as 10-bit data. During the set blanking period, theencoder 83B encodes (generates) 10-bit blanking data on the basis of the2-bit control signal input from the terminal 92, and the encoder 83Cencodes (generates) 10-bit blanking data on the basis of 2-bit dataindicating the superimposing period supplied from the superimposingperiod table 86. The output of the encoder 83B and the output of theencoder 83C are transmitted to the monitor 33 as an output of the datachannel B and an output of the data channel C, respectively.

In addition, the pixel clock generated by the PLL circuit 87 istransmitted to the monitor 33 as data of a clock channel.

FIG. 4 shows a configuration of the receiver 51. Decoders 101A to 101Creceive the 10-bit data of the data channels A to C, respectively,decode the 10-bit data, and then output the results as 8-bit data. Thedecoders 101A to 101C are supplied with a clock of a frequency ten timesthat of the pixel clock input to the clock channel in synchronizationwith the pixel clock, which clock of the frequency ten times that of thepixel clock is generated by a PLL circuit 106.

Eight-bit pixel data A or audio data decoded by the decoder 101A issupplied to a decrypting unit 102A. When the 10-bit blanking data isinput, the decoder 101A converts the 10-bit blanking data into 2-bithorizontal synchronizing data or vertical synchronizing data, and thensupplies the 2-bit horizontal synchronizing data or verticalsynchronizing data to the H/V sync generating unit 57.

Eight-bit pixel data B or audio data output by the decoder 101B issupplied to a decrypting unit 102B. When the 10-bit blanking data isinput, the decoder 101B converts the 10-bit blanking data into a 2-bitcontrol signal, and then supplies the 2-bit control signal to a controlunit 59 of the monitor 33.

Eight-bit pixel data C or audio data output by the decoder 101C issupplied to a decrypting unit 102C. When the 10-bit blanking data isinput, the decoder 101C converts the 10-bit blanking data into 2-bitdata indicating the superimposing period, and then supplies the 2-bitdata to a timing generating unit 103.

The decoders 101A to 101C also output the set blanking signal (DataEnable) indicating the set blanking period to the timing generating unit103. The timing generating unit 103 extends the set blanking period andthus generates a blanking signal of an original length by referring to asuperimposing period table 105 (the same table as the superimposingperiod table 86 in FIG. 2 is retained), and then outputs the blankingsignal to the H/V sync generating unit 57. The timing signal generatingunit 103 is supplied with a stabilized pixel clock (clock of the samefrequency as that of the pixel clock input to the terminal 95 of thetransmitter 43) generated by the PLL circuit 106 in synchronization withthe data of the clock channel. The timing generating unit 103 generatesa timing signal on the basis of these pieces of data input thereto, andsupplies the timing signal to the decrypting units 102A to 102C and abuffer 104.

The decrypting units 102A to 102C decrypt the 8-bit pixel data A oraudio data, the pixel data B or audio data, and the pixel data C oraudio data input thereto, respectively, and then output the pixel datato the D/A converter 55.

The 8-bit audio data decrypted by the decrypting units 102A to 102C issupplied to the buffer 104 to be converted into continuous data, andthen output to the D/A converter 52.

The blanking signal generated by the timing generating unit 103 issupplied to the H/V sync generating unit 57 in conjunction with thepixel clock of the frequency 1/10 that of the clock supplied to thedecoders 101A to 101C, which pixel clock is generated by the PLL circuit106 (clock of the same frequency as that of the pixel clock input to theterminal 95 of the transmitter 43 in FIG. 2).

The operation of the transmitting and receiving system will next bedescribed. When the front end 41 of the digital tuner 31 receives aradio wave of a channel specified by a user via the antenna 32, thefront end 41 of the digital tuner 31 demodulates the received signal,and then outputs the demodulated signal to the AV decoder 42. The AVdecoder 42 decodes the received signal input thereto, and then outputsdecoded audio data and video data to the transmitter 43. The transmitter43 multiplexes the audio data into the horizontal blanking period of thevideo data input thereto, and then outputs the result to the monitor 33via the TMDS 34.

The TMDS 34 is essentially an interface for personal computers, andtherefore is in a format not allowing transmission of audio data. Inthis case, however, the audio data is multiplexed into the blankingperiod of the video data, and therefore the audio data can betransmitted via the TMDS 34.

The receiver 51 on the monitor 33 side receives the video datatransmitted via the TMDS 34, separates the audio data inserted in theblanking period, and then outputs the audio data to the D/A converter52. The D/A converter 52 converts the audio data input thereto intoanalog audio signals for a left and a right channel to be output fromthe speakers 53 and 54.

Horizontal synchronizing data and vertical synchronizing data alsoextracted and generated from the blanking period by the receiver 51 aresupplied to the H/V sync generating unit 57. The H/V sync generatingunit 57 generates a horizontal synchronizing signal and a verticalsynchronizing signal on the basis of the data input thereto, and thenoutputs the horizontal synchronizing signal and the verticalsynchronizing signal to the driving circuit of the CRT 58.

The receiver 51 also outputs pixel data extracted from the data inputthereto to the D/A converter 55 to subject the pixel data to D/Aconversion. RGB signals output from the D/A converter 55 (signals of thepixel data A to C) are amplified by the RGB amplifier 56, and thensupplied to the CRT 58 for display. In this case, the CRT 58 iscontrolled in the scanning of scanning lines on the basis of thehorizontal synchronizing signal and the vertical synchronizing signalgenerated by the H/V sync generating unit 57.

Transmission processing on the channel A of the transmitter 43 in FIG. 2will next be described with reference to the flowchart of FIG. 5.

At a step S1, the timing generation unit 85 determines whether thetiming generation unit 85 is now in a blanking period on the basis ofinput from the terminal 94. When the timing generation unit 85 is not ina blanking period, the processing proceeds to a step S2, at which thetiming generation unit 85 generates a switch control signal and thenoutputs the switch control signal to the switch 81A to turn the switch81A to the upper input terminal (as viewed in FIG. 2). The switch 81Athereby selects the pixel data A input from the terminal 80A (B data ofRGB data, for example), and then supplies the pixel data A to theencrypting unit 82A.

At a next step S5, the encrypting unit 82A encrypts the data selected bythe switch 81A (pixel data A in this case). At a step S6, the encoder83A encodes the pixel data A encrypted by the encrypting unit 82A at thestep S5, and at a step S8, the encoder 83A outputs the encoded data tothe TMDS 34 as data of the data channel A.

When the timing generation unit 85 determines at the step S1 that thetiming generation unit 85 is now in a blanking period, on the otherhand, the processing proceeds to a step S3. At the step S3, the timinggeneration unit 85 refers to a table of the superimposing period table86 to determine whether the timing generation unit 85 is in a period forsuperimposing (multiplexing) audio data. Specifically, as describedabove, a period for superimposing audio data (superimposing data) in ahorizontal blanking period is predefined in the superimposing periodtable 86. The timing generation unit 85 determines on the basis of thedefinition whether the timing generation unit 85 is now in a period forsuperimposing (multiplexing) audio data.

When the timing generation unit 85 determines that the timing generationunit 85 is in a horizontal blanking period but not in a period forsuperimposing audio data, the processing proceeds to a step S7. At thestep S7, the timing generation unit 85 controls the encoder 83A togenerate 10-bit horizontal or vertical blanking data on the basis of2-bit horizontal or vertical synchronizing data input from the terminal91 and then output the 10-bit horizontal or vertical blanking data.

When the 2-bit data is denoted by (C1, C0), the encoder 83A outputs10-bit control (CTL) data provided for the 2-bit data as shown in FIG.6, for example, as the horizontal or vertical blanking data.

In the example of FIG. 6, when a 2-bit input is ‘00,’ the blanking datais ‘0010101011.’ When the input is ‘01,’ the blanking data is‘1101010100.’ When the input is ‘10,’ the blanking data is ‘0010101010.’When the input is ‘11,’ the blanking data is ‘1101010101.’ The 10-bitblanking data is predetermined as blanking data, and is unique data usedneither for video data (pixel data) nor for audio data.

Although the processing of the step S7 is basically performed over theentire blanking period, the processing of the step S7 in the presentinvention is performed only in a period when audio data is notsuperimposed. This means that the blanking period is set to a lengthshorter than the original period.

The step S7 is succeeded by a step S8, at which the encoder 83A outputsthe blanking data generated at the step S7 via the TMDS 34.

When the timing generation unit 85 determines at the step S3 that thetiming generation unit 85 is now in a period for superimposing audiodata, on the other hand, the processing proceeds to a step S4. At thestep S4, the timing generation unit 85 controls the switch 81A to turnthe contact of the switch 81A to the lower side (as viewed in FIG. 2).At this step S4, the switch 81A selects audio data supplied from thebuffer 84, and then outputs the audio data to the encrypting unit 82A.

At the step S5, the encrypting unit 82A encrypts the audio data inputvia the switch 81A, and then outputs the encrypted audio data to theencoder 83A. At the step S6, the encoder 83A encodes the encrypted audiodata input from the encrypting unit 82A, and at the step S8, the encoder83A outputs the encoded data to the TMDS 34. Thus, the video data (pixeldata) and the audio data are encrypted by the common encrypting unit82A. It is therefore possible to simplify the configuration, miniaturizethe apparatus, and lower the cost as compared with a case where thevideo data (pixel data) and the audio data are provided as data separatefrom each other.

Transmission processing on the channel B will next be described withreference to the flowchart of FIG. 7.

The processing at steps S21 to S28 in FIG. 7 is basically the same asthe processing at the steps S1 to S8 in the transmission processing ofthe channel A shown in FIG. 5. However, the pixel data selected by theswitch 81B at the step S22 is pixel data B, and the data encrypted bythe encrypting unit 82B at the step S25 is the pixel data B or the audiodata supplied from the buffer 84 selected by the switch 81B.

In addition, at the step S27, the encoder 83B generates 10-bithorizontal or vertical blanking data (FIG. 6) on the basis of the 2-bitcontrol signal supplied from the terminal 92.

The other processing is the same as in FIG. 5.

Transmission processing on the channel C is as shown in FIG. 8.Processing at steps S31 to S38 is basically the same as the processingat the steps S1 to S8 in the flowchart of FIG. 5. However, the dataselected by the switch 81C at the step S32 and encrypted by theencrypting unit 82C at the step S35 is pixel data C supplied from theterminal 80C or the audio data supplied from the buffer 84. At the stepS37, the encoder 83C generates 10-bit horizontal or vertical blankingdata (FIG. 6) on the basis of 2-bit data indicating a superimposingperiod supplied from the superimposing period table 86.

The processing described above will be described further with referenceto the timing charts of FIGS. 9A, 9B, 9C, and 9D. As shown in FIG. 9A, ablanking signal is generated in a cycle of a horizontal scanning line.As described above, the period of the horizontal blanking signalcorresponds to 138 pixels in the case of 480p pixel data, 370 pixels inthe case of 720p pixel data, and 280 pixels in the case of 1080i pixeldata.

As shown in FIG. 9B, a first period T₁ of the blanking period T₀ is atransmitting blanking period, and a remaining period T₂ of the blankingperiod T₀ is a period for multiplexing audio data.

The audio data, which is continuous data as shown in FIG. 9D, iscompressed with respect to a time axis by being encoded by the encoders83A to 83C, and multiplexed into the period T₂ as shown in FIG. 9C.

FIGS. 10A, 10B, and 10C show in enlarged dimension data around ablanking period of the channel A. As shown in FIG. 10B, although theperiod of an original blanking signal is T₀, the blanking signal ismultiplexed in a manner as shown in FIG. 10A and FIG. 10C only in aperiod T₁ within the period T₀. This means that the blanking signal is,as it were, shortened from the period T₀ to the period T₁. Audio data ismultiplexed into a remaining superimposing period T₂ obtained bysubtracting the period T₁ from the period T₀. In other words, audio datais multiplexed as data similar to pixel data. In order to distinguishaudio data from pixel data on the receiving part, however,distinguishing data indicating the superimposing period T₂ istransmitted in the period T₁ on the channel C, as described above.

FIGS. 11A, 11B, and 11C show the arrangement of data around a blankingperiod of the channel B. FIGS. 12A, 12B, and 12C show the arrangement ofdata around a blanking period of the channel C.

In the period T₁, horizontal synchronizing data or verticalsynchronizing data is transmitted in the example of FIGS. 10A, 10B, and10C, whereas a control signal is transmitted in the example of FIGS.11A, 11B, and 11C, and table distinguishing data is transmitted in theexample of FIGS. 12A, 12B, and 12C. That is, as described above,blanking data inserted in the period T₁ is data representing thehorizontal or vertical synchronizing data (for the channel A), thecontrol signal (for the channel B), or the table distinguishing data(for the channel C).

The receiving processing of the channel A of the receiver 51 in FIG. 4will next be described with reference to the flowchart of FIG. 13. At astep S41, the decoder 101A decodes data input thereto.

At a step S42, the decoder 101A determines whether the decoded data isblanking data. When the decoder 101A determines that the decoded data isblanking data, the processing proceeds to a step S43, at which thedecoder 101A generates horizontal or vertical synchronizing data(generates 2-bit data corresponding to the 10-bit control code in FIG.6) on the basis of the blanking data, and then outputs the horizontal orvertical synchronizing data to the H/V sync generating unit 57.

The decoder 101A also outputs data of a period corresponding to theblanking data as data of a set blanking period to the timing generatingunit 103. As will be described in detail in the processing at a step S83in FIG. 15, the timing generating unit 103 corrects (lengthens) the setblanking period to thereby generate a blanking signal of originallength.

When the decoder 101A determines at the step S42 that the decoded datais not blanking data, the data is either pixel data or audio data.Therefore, the decoder 101A outputs the data to the decrypting unit102A. At a step S44, the decrypting unit 102A decrypts the data inputthereto. The decrypting unit 102A determines whether the decrypted datais audio data on the basis of a timing signal from the timing generatingunit 103 at a step S45. When the decrypting unit 102A determines thatthe decrypted data is audio data, the processing proceeds to a step S46,at which the audio data is supplied to the buffer 104 to be storedtherein.

Specifically, the timing generating unit 103 reads a superimposingperiod T₂ corresponding to table distinguishing data for distinguishingthe superimposing period, which data is output by the decoder 101C, fromthe superimposing period table 105 on the basis of the tabledistinguishing data. The timing generating unit 103 then outputs atiming signal corresponding to the period T₂. The decrypting unit 102Adetermines that data in the period T₂ is audio data.

The buffer 104 is also supplied with audio data decrypted by thedecrypting unit 102B or 102C of the channel B or the channel C. Thebuffer 104 outputs these pieces of audio data as continuous data.

When the decrypting unit 102A determines at the step S45 that thedecrypted data is not audio data (when the decrypting unit 102Adetermines that the decrypted data is pixel data A), on the other hand,the processing proceeds to a step S47, at which the decrypting unit 102Aoutputs the data to the D/A converter 55.

FIG. 14 shows the receiving processing of the channel B. The processingat steps S61 to S67 is basically the same as shown in the flowchart ofFIG. 13. However, at the step S63, the decoder 101B generates a controlsignal rather than horizontal synchronizing data or verticalsynchronizing data on the basis of blanking data. The control signal isoutput to the control unit 59.

The flowchart of FIG. 15 shows the receiving process of the channel C ofthe receiver 51. The processing at steps S81 to S87 in FIG. 15 isbasically the same as the processing at the steps S41 to S48 in FIG. 13.However, the processing at the step S83 in FIG. 15 is different from theprocessing at the step S43 in FIG. 13. Specifically, at the step S83 inFIG. 15, the decoder 101C generates 2-bit table distinguishing data onthe basis of 10-bit blanking data. The table distinguishing data, whichallows the superimposing period T₂ to be identified, is supplied to thetiming generating unit 103.

The timing generating unit 103 reads from the superimposing period table105 the superimposing period T₂ corresponding to the tabledistinguishing data supplied from the decoder 101C, and then sets theperiod T₂ in an internal memory. The timing generating unit 103generates a timing signal for separating audio data from pixel data byusing the superimposing period T₂ until new table distinguishing data isreceived in a next vertical blanking period.

In addition, the timing generating unit 103 lengthens (corrects) the setblanking period T₁ by the period T₂ on the basis of the set blankingdata supplied from the decoders 101A to 101C and the set superimposingperiod T₂. The timing generating unit 103 generates a blanking signalcorresponding to the blanking period T₀ of original length, and thenoutputs the blanking signal to the H/V sync generating unit 57.

The receiving processing described above will be described further withreference to the timing charts of FIGS. 16A, 16B, 16C, and 16D. As shownin FIG. 16A, blanking data is transmitted in a state of being insertedin only the period T₁ of the blanking period T₀. This means that theblanking period T₀ is transmitted in a state of being shortened to theset blanking period T₁, as shown in FIG. 16B. If the blanking period T₀remains in this state, audio data inserted in the period T₂ is processedas pixel data. Thus, as shown in FIG. 16C, the timing generating unit103 lengthens (corrects) the set blanking period T₁ by the period T₂ tothereby generate a correct blanking period, or the period T₀ of originallength, and then outputs the blanking period to the H/V sync generatingunit 57.

As shown in FIG. 16D, the buffer 104 converts divided audio datasupplied from the decrypting units 102A to 102C into continuous audiodata, and then outputs the continuous audio data to the D/A converter52.

The processing of inserting table distinguishing data into the period T₁as shown in FIGS. 12A, 12B, and 12C needs to be performed in everyhorizontal blanking period when the value of the superimposing period T₂is changed for each horizontal scanning line. Usually, however, thesuperimposing period T₂ is not changed frequently. In such a case, tabledistinguishing data may be multiplexed into only a vertical blankingperiod.

In the embodiment of FIG. 1, the transmitter 43 of the digital tuner 31on the transmitting side and the receiver 51 of the monitor 33 on thereceiving side retain the superimposing period table 86 and thesuperimposing period table 105, respectively, and table distinguishingdata for indicating which of the tables retained in the superimposingperiod table 86 and the superimposing period table 105 is to be used isinserted in the blanking period T₁ of the channel C. However, the tabledistinguishing data may be transmitted from the digital tuner 31 side tothe monitor 33 side via the DDC 35, for example, forming a transmissionline separate from the TMDS 34.

The series of processing steps described above may be carried out notonly by hardware but also by software. In such a case, the digital tuner31 is formed as shown in FIG. 17, for example.

A CPU (Central Processing Unit) 221 in FIG. 17 performs variousprocessing according to programs stored in a ROM (Read Only Memory) 222or programs loaded from a storage unit 228 into a RAM (Random AccessMemory) 223. The RAM 223 also stores signals and the like necessary forthe CPU 221 to perform various processing, as required.

The CPU 221, the ROM 222, and the RAM 223 are connected to each othervia a bus 224. The bus 224 is also connected with an input/outputinterface 225.

The input/output interface 225 is connected with an input unit 226formed by a keyboard, a mouse and the like, an output unit 227 formed bya display formed by a CRT, an LCD or the like and a speaker or the like,the storage unit 228 formed by a hard disk or the like, and acommunication unit 229 formed by a modem, a terminal adapter or thelike. The communication unit 229 performs processing for communicationvia a network.

When necessary, the input/output interface 225 is also connected with adrive 230 to which a magnetic disk 241, an optical disk 242, amagneto-optical disk 243, a semiconductor memory 244 or the like isinserted as required. Computer programs read from the magnetic disk 241,the optical disk 242, the magneto-optical disk 243, the semiconductormemory 244 and the like are installed in the storage unit 228 asrequired.

Though not shown in the figure, when the series of processing steps isto be carried out by software, the receiver 51 and the like may also beformed by a computer as with the digital tuner 31. When the series ofprocessing steps is to be carried out by software, a program forming thesoftware is installed from a network or a recording medium onto acomputer that is incorporated in special hardware, or a general-purposepersonal computer that can perform various functions by installingvarious programs thereon, for example.

Examples of the recording medium include not only program-recordedpackaged media distributed to users to provide the program separatelyfrom the apparatus proper, which packaged media are formed by magneticdisks 241 (including floppy disks), optical disks 242 (including CD-ROM(Compact Disk-Read Only Memory) and DVD (Digital Versatile Disk)),magneto-optical disks 243 (including MD (Mini-Disk)), or semiconductormemories 244 as shown in FIG. 17, but also the hard disk included in thestorage unit 228 and the ROM 222 storing the program, which are suppliedto the user in a state of being preincorporated in the apparatus proper.

It is to be noted that in the present specification, the stepsdescribing the program recorded on a recording medium include not onlyprocessing steps carried out in time series in the described order, butalso processing steps carried out in parallel or individually and notnecessarily in time series.

Also, in the present specification, a system denotes the whole apparatusformed by a plurality of apparatus.

As described above, the apparatus and method for informationtransmission, and the program according to the present inventionmultiplex a compressed audio signal into a differential period createdby setting a blanking period to a predetermined period. It is thereforepossible to transmit an audio signal efficiently.

The apparatus and method for information reception, and the programaccording to the present invention capture the compressed audio signalmultiplexed in the multiplexing period of a captured video signal, andcorrect the blanking period on the basis of the multiplexing period. Itis therefore possible to reliably extract the compressed audio signal,recover the length of the original blanking period readily and reliably,and thereby prevent adverse effects on reproduction of the video signal.

According to the system and method for information transmission andreception, and the program according to the present invention, theinformation transmitting apparatus multiplexes a compressed audio signalinto a differential period created by setting a blanking period of avideo signal to a predetermined period, and thereby transmits thecompressed audio signal, and the information receiving apparatuscaptures the compressed audio signal multiplexed in the differentialperiod, and corrects the blanking period. Therefore, it is possible totransmit and receive the compressed audio signal other than the videosignal readily and reliably in a system capable of transmitting andreceiving a video signal, and thus realize a system having no adverseeffects on transmission and reception of an original video signal.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A data transmission apparatus comprising: a first input unit forinputting video data of a predetermined number of bits; a second inputunit for inputting audio data; a setting unit for setting, within ablanking period of the video data, a setup period that is shorter thanthe blanking period; a multiplexing unit for multiplexing the audio datainto a superimposing period, the superimposing period occurring withinthe blanking period and not including the setup period, and the setupperiod at least preceding the superimposing period; and a video datatransmitting unit for encoding the video data to generate encoded videodata having a number of bits greater than the predetermined number ofbits and transmitting the encoded video data to a data channel; thesetup period being used to convey predetermined data other than videodata or audio data; and the predetermined data comprising informationfor identifying the encoded video data and the superimposing period. 2.A data transmission apparatus as claimed in claim 1, wherein the settingunit sets the setup period by disposing a blanking signal representingthe blanking period only during the setup period and not during thesuperimposing period.
 3. A data transmission apparatus as claimed inclaim 2, wherein the blanking signal forms a control signal.
 4. A datatransmission apparatus as claimed in claim 1, further comprising aretaining unit for retaining information on the setup period or thesuperimposing period, wherein the multiplexing unit multiplexes theaudio data into the superimposing period on the basis of the informationretained by the retaining unit.
 5. A data transmission apparatus asclaimed in claim 4, wherein the retaining unit retains a correspondencebetween a type of the video data and the setup period or superimposingperiod as the information on the setup period or superimposing period.6. A data transmission apparatus as claimed in claim 1, furthercomprising a distinguishing information transmitter for transmittingdistinguishing information for distinguishing the setup period or thesuperimposing period.
 7. A data transmission apparatus as claimed inclaim 6, wherein the distinguishing information transmitter transmitsthe distinguishing information in the setup period of the video data asa type of blanking signal representing a blanking period.
 8. A datatransmission apparatus as claimed in claim 7, wherein the distinguishinginformation transmitter transmits the distinguishing information in avertical blanking period.
 9. A data transmission apparatus as claimed inclaim 6, wherein the distinguishing information transmitter transmitsthe distinguishing information via a transmission line different from atransmission line of the encoded video data.
 10. A data transmissionapparatus as claimed in claim 6, wherein the distinguishing informationis information allowing determination of a period from a start point toan end point of the setup period or a period from a start point to anend point of the superimposing period.
 11. A data transmission apparatusas claimed in claim 1, further comprising a compressing unit forcompressing the audio data.
 12. A data transmission apparatus as claimedin claim 1, further comprising an encrypting unit for encrypting theaudio data by a method common with the video data.
 13. An informationtransmission method comprising: inputting video data of a predeterminednumber of bits; inputting audio data; setting, within a blanking periodof the video data, a setup period that is shorter than the blankingperiod; multiplexing the audio data into a superimposing period, thesuperimposing period occurring within the blanking period and notincluding the setup period, and the setup period at least preceding thesuperimposing period; and encoding the video data to generate encodedvideo data having a number of bits greater than the predetermined numberof bits, and transmitting the encoded video data to a data channel; thesetup period being used to convey predetermined data other than videodata or audio data; and the predetermined data comprising informationfor identifying the encoded video data and the superimposing period. 14.A computer-readable medium storing a computer-readable program, theprogram being operable to perform an information transmission methodcomprising: inputting video data of a predetermined number of bits;inputting audio data; setting, within a blanking period of the videodata, a setup period that is shorter than the blanking period;multiplexing the audio data into a superimposing period, thesuperimposing period occurring within the blanking period and notincluding the setup period, and the setup period at least preceding thesuperimposing period; and encoding the video data to generate encodedvideo data having a number of bits greater than the predetermined numberof bits, and transmitting the encoded video data to a data channel; thesetup period being used to convey predetermined data other than videodata or audio data; and the predetermined data comprising informationfor identifying the encoded video data and the superimposing period. 15.A system for performing an information transmission process comprising:a processor for executing instructions; and instructions, theinstructions including instructions for inputting video data of apredetermined number of bits; inputting audio data; setting, within ablanking period of the video data, a setup period that is shorter thanthe blanking period; multiplexing the audio data into a superimposingperiod, the superimposing period occurring within the blanking periodand not including the setup period, and the setup period at leastpreceding the superimposing period; and encoding the video data togenerate encoded video data having a number of bits greater than thepredetermined number of bits, and transmitting the encoded video data toa data channel; the setup period being used to convey predetermined dataother than video data or audio data; and the predetermined datacomprising information for identifying the encoded video data and thesuperimposing period.
 16. An information receiving apparatus comprising:a receiver for receiving a transmitted signal; a first capturing unitfor capturing video data from the received signal; a detecting unit fordetecting a blanking period of the captured video data, the blankingperiod being set to a duration different from the duration of anoriginal blanking period of the video data; a second capturing unit forcapturing information on a superimposing period of the received signalin which audio data is multiplexed, the superimposing period occurringwithin the original blanking period and not including the blankingperiod of the captured video data, and the blanking period of thecaptured video data at least preceding the superimposing period; a thirdcapturing unit for capturing the audio data from the received signal onthe basis of the captured information and superimposing period; and acorrecting unit for correcting the detected blanking period on the basisof the captured information on the superimposing period; data indicativeof the duration of the superimposing period being received during theblanking period of the captured video data.
 17. An information receivingapparatus as claimed in claim 16, further comprising a converting unitfor converting the audio data captured by the third capturing unit intoa continuous signal.
 18. An information receiving apparatus as claimedin claim 16, wherein a blanking signal representing the blanking periodof the captured video data forms a control signal.
 19. An informationreceiving apparatus as claimed in claim 16, further comprising aretaining unit for retaining the information on the superimposingperiod, wherein the second capturing unit captures the information onthe superimposing period from the information retained by the retainingunit.
 20. An information receiving apparatus as claimed in claim 19,wherein the retaining unit retains a correspondence between a type ofthe video data and the superimposing period as the information on thesuperimposing period.
 21. An information receiving apparatus as claimedin claim 16, further comprising a distinguishing information extractingunit for extracting distinguishing information for distinguishing thesuperimposing period.
 22. An information receiving apparatus as claimedin claim 21, wherein the distinguishing information extracting unitextracts the distinguishing information from a blanking signalrepresenting the blanking period of the captured video data, theblanking signal being inserted in the blanking period of the capturedvideo data.
 23. An information receiving apparatus as claimed in claim22, wherein the distinguishing information extracting unit extracts thedistinguishing information from the blanking signal in a verticalblanking period.
 24. An information receiving apparatus as claimed inclaim 21, wherein the distinguishing information extracting unitextracts the distinguishing information from a signal received via atransmission line different from a transmission line of the capturedvideo data.
 25. An information receiving apparatus as claimed in claim21, wherein the distinguishing information is information allowingdetermination of a period from a start point to an end point of thesuperimposing period or a period from a start point to an end point ofthe blanking period of the captured video data.
 26. An informationreceiving apparatus as claimed in claim 16, wherein the audio data iscompressed audio data, and further comprising an expanding unit forexpanding the compressed audio data.
 27. An information receivingapparatus as claimed in claim 16, further comprising a decrypting unitfor decrypting the audio data by a method common with the video data,the audio data being encrypted by a method common with the video data.28. An information receiving method comprising: receiving a transmittedsignal; capturing video data from the received signal; detecting ablanking period of the captured video data, the blanking period beingset to a duration different from the duration of an original blankingperiod of the video data; capturing information on a superimposingperiod of the received signal in which audio data is multiplexed, thesuperimposing period occurring within the original blanking period andnot including the blanking period of the captured video data, and theblanking period of the captured video data at least preceding thesuperimposing period; capturing the audio data from the received signalon the basis of the captured information and superimposing period; andcorrecting the detected blanking period on the basis of the capturedinformation on the superimposing period; data indicative of the durationof the superimposing period being received during the blanking period ofthe captured video data.
 29. A computer-readable medium storing acomputer-readable program, the program being operable to perform aninformation receiving method comprising: receiving a transmitted signal;capturing video data from the received signal; detecting a blankingperiod of the captured video data, the blanking period being set to aduration different from the duration of an original blanking period ofthe video data; capturing information on a superimposing period of thereceived signal in which audio data is multiplexed, the superimposingperiod occurring within the original blanking period and not includingthe blanking period of the captured video data, and the blanking periodof the captured video data at least preceding the superimposing period;capturing the audio data from the received signal on the basis of thecaptured information and superimposing period; and correcting thedetected blanking period on the basis of the captured information on thesuperimposing period; data indicative of the duration of thesuperimposing period being received during the blanking period of thecaptured video data.
 30. A system for performing an informationreceiving process comprising: a processor for executing instructions;and instructions, the instructions including instructions for receivinga transmitted signal; capturing video data from the received signal;detecting a blanking period of the captured video data, the blankingperiod being set to a duration different from the duration of anoriginal blanking period of the video data; capturing information on asuperimposing period of the received signal in which audio data ismultiplexed, the superimposing period occurring within the originalblanking period and not including the blanking period of the capturedvideo data, and the blanking period of the captured video data at leastpreceding the superimposing period; capturing the audio data from thereceived signal on the basis of the captured information andsuperimposing period; and correcting the detected blanking period on thebasis of the captured information on the superimposing period; dataindicative of the duration of the superimposing period being receivedduring the blanking period of the captured video data.
 31. Aninformation transmitting and receiving system comprising: a first inputunit for inputting video data of a predetermined number of bits; asecond input unit for inputting audio data; a setting unit for setting,within a blanking period of the video data, a setup period that isshorter than the blanking period; a multiplexing unit for multiplexingthe audio data into a superimposing period, the superimposing periodoccurring within the blanking period and not including the setup period,and the setup period at least preceding the superimposing period; avideo data transmitting unit for encoding the video data to generateencoded video data having a number of bits greater than thepredetermined number of bits and transmitting the encoded video data toa data channel; the setup period being used to convey predetermined dataother than video data or audio data; and the predetermined datacomprising information for identifying the encoded video data and thesuperimposing period; a first capturing unit for capturing the encodedvideo data from the data channel; a second capturing unit for capturingthe predetermined data; and a third capturing unit for capturing theaudio data on the basis of the predetermined data.
 32. An informationtransmitting and receiving method comprising: inputting video data of apredetermined number of bits; inputting audio data; setting, within ablanking period of the video data, a setup period that is shorter thanthe blanking period; multiplexing the audio data into a superimposingperiod, the superimposing period occurring within the blanking periodand not including the setup period, and the setup period at leastpreceding the superimposing period; encoding the video data to generateencoded video data having a number of bits greater than thepredetermined number of bits, and transmitting the encoded video data toa data channel; the setup period being used to convey predetermined dataother than video data or audio data; and the predetermined datacomprising information for identifying the encoded video data and thesuperimposing period; capturing the encoded video data from the datachannel; capturing unit for capturing the predetermined data; andcapturing the audio data on the basis of the predetermined data.
 33. Acomputer-readable medium storing a computer-readable program, theprogram being operable to perform an information transmitting andreceiving method comprising: inputting video data of a predeterminednumber of bits; inputting audio data; setting, within a blanking periodof the video data, a setup period that is shorter than the blankingperiod; multiplexing the audio data into a superimposing period, thesuperimposing period occurring within the blanking period and notincluding the setup period, and the setup period at least preceding thesuperimposing period; encoding the video data to generate encoded videodata having a number of bits greater than the predetermined number ofbits, and transmitting the encoded video data to a data channel; thesetup period being used to convey predetermined data other than videodata or audio data; and the predetermined data comprising informationfor identifying the encoded video data and the superimposing period;capturing the encoded video data from the data channel; capturing unitfor capturing the predetermined data; and capturing the audio data onthe basis of the predetermined data.
 34. An system for performing aninformation transmitting and receiving process comprising: a processorfor executing instructions; and instructions, the instructions includinginstructions for inputting video data of a predetermined number of bits;inputting audio data; setting, within a blanking period of the videodata, a setup period that is shorter than the blanking period;multiplexing the audio data into a superimposing period, thesuperimposing period occurring within the blanking period and notincluding the setup period, and the setup period at least preceding thesuperimposing period; encoding the video data to generate encoded videodata having a number of bits greater than the predetermined number ofbits, and transmitting the encoded video data to a data channel; thesetup period being used to convey predetermined data other than videodata or audio data; and the predetermined data comprising informationfor identifying the encoded video data and the superimposing period;capturing the encoded video data from the data channel; capturing unitfor capturing the predetermined data; and capturing the audio data onthe basis of the predetermined data.